Fellow PT blogger Michael Castleman recently raised the question of how common masturbation really is. He cited a study that seems to show it's less prevalent than conventionally thought. In the study, people were asked, in person, about their auto-erotic habits. Castleman acknowledges that this might be a bit awkward, writing, "It's possible that the face-to-face format suppressed response. Some people might not have admitted masturbating to an interviewer. But even allowing for this possibility, it seems clear that masturbation is by no means as prevalent … as many people believe."

There's good reason to believe Castleman may well be underestimating the importance of this very weak point in the study he cites.

One of the long-standing mysteries of human sexuality has been that heterosexual men tend to report having more sexual encounters and partners than heterosexual women – a mathematical impossibility. This was chalked up to men’s tendency to exaggerate upward and women’s to exaggerate downward in recalling such information. Psychologists Terri Fisher and Michele Alexander decided to take a closer look at people’s claims regarding age of first sexual experience, number of partners, and frequency of sexual encounters. Fisher and Alexander set up three different testing conditions:

1. Where subjects were led to believe their answers might be seen by the researchers, who waited just outside the room;2. Where the subjects could answer the questions privately and anonymously;3. Where the subjects had electrodes placed on their hand, arm, and neck – believing themselves (falsely) to be hooked up to a polygraph that would detect lies.

Women who thought their answers might be seen reported an average of 2.6 sexual partners (all the subjects were college students younger than 25). Those who thought their answers were anonymous reported 3.4 partners, while those who thought their lies would be detected reported an average of 4.4 partners. While the women admitted to 70% more sexual partners when they thought they couldn’t fib, the men’s answers showed almost no variation.

Sex researchers, physicians, psychologists (and parents) must never forget that the answers you’re likely to get from women may depend very much on when, where, and how the question is asked, and who’s asking.

Do you know the variance was in women's reports? Was the problem that almost all women were underreporting their number of sexual partners, or was it just a few with quite high numbers who were ashamed to admit it?

Interesting question, Andy, and always a good idea to question the methodology underlying any research. But I think in this case, the researchers weren't comparing the women's answers to any objective reality, so much as comparing the answers of women under the different conditions. Nobody knows how many lovers the women "really" had; just that those who thought they could get away with lying claimed (on average) far fewer. This is not to say that any of the individual women were necessarily lying, just that the more likely it seemed that they could get away with lying, the lower their numbers were.

I agree with your points. However, the argument you cited is rather week. I followed the link you posted:

"The study involved 201 unmarried, heterosexual college students (96 men and 105 women) between the ages of 18 and 25."

American college students are not a really representative poll for the study in question, in my opinion, or for most other studies, for that matter. This already lowers the value of the study you referred to in my eyes. Do you know of any other studies that would support your point?

I agree completely with your point that American college students aren't representative of the overall population. In fact, we make that very point in our book. Unfortunately, however, ease of access seems to trump scientific validity in a lot of research, as the vast majority of studies done on human sexuality are conducted by graduate students, using undergrads as their subjects. It's a huge problem in sexuality research, but one that few people really want to talk about much. You're wise to discount the value of such studies.

Having said that, I'm afraid I don't have any similar study at hand that uses as more representative sample group.

I actually worked on a different U of C study in the 80's and would like to point out that while the entire survey may have been face to face the most sensitive questions such as on masturbation rates may have been handed to respondents on a handout card, seperate from the larger survey form and then given back to the surveyor in a sealed envelope or mailed back seperately. Since cash incentives are sometimes used on these types of surveys they would often be conducted in a neutral location near a mailbox so the respondent could be sure the interviewer did not have access to their most sensitive data. Reducing some bias concerns.

Generally, the U of C and NORC go to extreme measures to try to ensure that as many possible sources of bias as possible are eliminated. At least in the past, NORC surveyors went through a week's training in survey techniques and theory including testing before being allowed in the field under CLOSE field supervision to do even a screening survey to select respondents to be interviewed.

The issue of reluctance to admit actual practice in a survey like this is a real problem. In many ways you may have to treat the rates of masterbation as questionable and use any yes answer as a positive but be somewhat sceptical of no answers when known potential sources of bias exist.

For example, a member of a religious group that believes that masterbation is wrong may say they don't masterbate because they never do or because they sometimes do but are ashamed to admit it or frequently do but are ashamed to admit it.

Members of certain occupations such as teachers and ministers might fear being outed and not reveal their practice. Does that mean the results are useless? Hardly? They suggest a truth if not the absolute truth we would hope for. Whether it is differences in practice or reporting may require a different kind of study with direct observation of practice to reveal. But that gets into the trade-off between quantitative studies and qualitative studies and brings in many other issues.